2020 Volume 60 Issue 1 Pages 99-105
Control of the solidification microstructure in continuous casting of steel is necessary because the microstructure affects material properties. In order to predict the solidification microstructure, the effect of dendrite fragmentation was indirectly introduced in the cellular automaton method by using Vcrit, which is the velocity threshold of the molten steel flow. Calculations were carried out with various Vcrit (200 µs−1 ≦ Vcrit ≦ 1 mms−1), and the results were compared with the results of a casting experiment using high carbon steel. The observed specimens were extracted from the upper part and lower part of casting. Equiaxed grains and branched columnar grains were observed in the microstructure of the upper specimen, whereas only columnar grains were observed in the microstructure of the lower specimen. The calculation results with Vcrit greater than 400 µm showed good qualitative agreement with the microstructures of both observed specimens. The microstructures were calculated because the flow velocity of the molten steel around the upper specimen was much greater than that around the lower specimen. There is a possibility that solute transportation, which induces fragmentation, occurs even if the velocity of the molten steel flow is on the order of 10−4 ms−1.
